Highly sensitive short-range mode resonance sensor with multilayer structured hyperbolic metamaterials.

Hyperbolic metamaterial (HMM) based sensors can achieve superior sensing performance than conventional surface plasmon resonance sensors. In this work, the operator approach to effective medium approximation (OEMA) is used to characterize the HMM dielectric constant properties of metal-dielectric multilayer structures, which are classified into short-range (SR) mode and long-range (LR) mode according to the propagation length of the bulk high K waves in HMM. The dispersion relations of SR modes are derived, and a high-sensitivity refractive index sensor is designed for the near-infrared SR mode resonance. The effects of the number of periods, cell thickness, metal fill rate and incidence angle on the SR mode resonance were analyzed for the multilayer structured HMM. Our designed sensing structure achieves a maximum sensitivity of 330 µm/RIU in the near-infrared band with a quality factor of 492 RIU-1. In addition, the simulations show that the SR mode resonance wavelength is flexible and tunable. We believe that the study of HMM-based SR mode resonance sensors offers potential applications for high-sensitivity biochemical detection.

Theoretical modeling and investigations of lossy mode resonance prism sensor based on TiO2 film.

The optical sensor based on lossy mode resonance can overcome the limitations of traditional surface plasmon resonance sensors and work under TE and TM polarized light. In this paper, an LMR sensor theoretical model with the configuration of prism/matching layer/lossy layer/sensing layer is proposed, which is based on the principle of attenuated total reflection. By using TiO2 film as the lossy layer and LiF film as the matching layer, the resonance signal under angle interrogation is effectively improved. One of the advantages of the proposed sensor is that the detection range and detection accuracy are dynamically adjustable, which provides additional degrees of freedom in the design and use of the device. The structural parameters (film thickness, layer refractive index) affecting the resonance signal have been investigated based on the electric field distribution at resonance and the coupled mode theory. The LMR signal under TE and TM polarization can be switched by changing the thickness ratio of the matching layer and the lossy layer. All possible combinations of film thicknesses are given as a reference for the design of the LMR prism sensor based on TiO2 film. Under proper thickness combination, the proposed sensor is capable of detecting the medium with refractive index ranging from 1.32 ∼ 1.47, with a sensitivity range of 34 ∼ 148 °/RIU under angle interrogation and a maximum value of 192 RIU-1 for FOM under TM polarization. We hope these investigations can prove the advantages of LMR prism sensors and provide guidance for the experimental implementation of LMR prism sensors in the future.